Health-Related Quality of Life (HRQoL) in Patients with Diffuse Large B-Cell Lymphoma (DLBCL) Treated with Polatuzumab Vedotin, Rituximab, Cyclophosphamide, Doxorubicin and Prednisone (Pola-R-CHP) Versus Rituximab, Cyclophosphamide, Doxorubicin, Vincristin